1. Field of the Invention
The invention relates to a lawnmower and, more particularly, to a self-propelled lawnmower that a user stands upon while operating.
2. Discussion of the Related Art
Lawnmowers equipped with dual hydraulically-powered drive systems that propel the drive wheels on each side of the mower are known in the lawn grooming or lawn care industries. Turning is achieved by driving each drive wheel at different speeds. They can even be turned in different directions for a very sharp or even a “zero-turn” radius, where the mower pivots about the midpoint drive wheel axis. Such zero-turn mowers can be configured as walk-behind, riders, or stand-on versions. For many implementations, the stand-on versions of zero-turn mowers prove more desirable.
For example, a user of a stand-on zero-turn mower does not have to expend energy walking, as required when using walk-behind mowers, which can be beneficial when mowing large expanses of land. As another example, a user of a stand-on zero-turn mower does not have to climb into and out of a seat that is mounted above a mower deck, as required when using rider mowers, which can be important when mowing areas with accumulated debris that must be removed manually and frequently. In other words, a user of a stand-on zero-turn mower can quickly mount and dismount the mower by merely stepping onto or off from a riding platform.
Several such riding platforms are known, all of which are at least partially suitable for their intended uses, while having at least some disadvantages.
For example, U.S. Pat. Nos. 5,507,138; 5,600,944; and 5,765,347 all entitled “Power Mower with Riding Platform for Supporting Standing-operator,” disclose riding platforms that support standing occupants or operators. Each riding platform is located between the hydraulic motors which rotate first and second rear drive wheels. In this configuration, the operator stands directly over a central turning point or turning axis of the stand-on mower, whereby the operator is unaffected by centrifugal forces created while turning the mower.
Notwithstanding the advantages of, e.g., imparting no centrifugal forces to an operator, stand-on mowers with riding platforms positioning operators upon turning axes have numerous drawbacks. A drawback of this type of riding platform is that the width dimension is limited by the space between the hydraulic motors that extend axially from the wheels, inwardly toward the operator. Or, if the riding platform extends underneath the hydraulic motors so that the platform is wider than the space between them, then the usable width of the riding platform is limited by the space between the hydraulic motors. Riding platforms that position operators directly upon turning axes will have either actual widths, or usable widths, that correspond to distances between the respective ends of the hydraulic motors. By limiting the actual and/or usable widths of riding platforms in such a manner, the overall usable surface area of each riding platform is correspondingly reduced or limited, which can hinder foot maneuverability or limit the number of standing positions. This can cause or aggravate operator fatigue during extended periods of use.
Another drawback is that the operators have limited options for laterally adjusting their foot position which at times requires them to assume a relatively narrower stance than they desire. For example, when mowing across a side hill, an operator can experience sensations of being unbalanced or unstable if they assume an overly narrow foot placement stance. In response, operators tend to pull against, push against, or otherwise utilize the mower hand controls to stabilize themselves, which can unduly stress the hand controls, reducing their use life.
Another drawback experienced during off-camber mowing, such as when mowing across a side hill, is that the drive wheel that is elevated, or on the high side of the hill, can lose traction because not enough weight of the machine or operator is transferred through it to the ground. Some attempts have been made to reduce such traction loss at the upper wheels by, for example, providing elevated narrow platforms laterally outside of the riding platform, yet still between the drive wheels. However, using such elevated platforms requires operators to position their feet at different heights or on different planes which can at times be awkward. Positioning these platforms in alignment with the turning axis also does nothing toward solving a related problem resulting from locating the center of gravity relatively close to the front wheels, which makes turning more difficult. For ideal turning, the center of gravity of the machine as a whole should be closer to the rear turning radius than is the case on previously available stand-on lawnmowers. This is most easily observed when traveling on a side hill in which gravity acting on the front of the lawnmower tends to pull the front of the vehicle downhill.
Another drawback is that these types of riding platforms position the operators' feet immediately adjacent the hydraulic motors. If the operators place their feet at the outer lateral edges of the riding platforms, then their feet will either touch or nearly touch portions of the hydraulic motors. This can be problematic because during use, hydraulic motors can become very warm or hot, whereby the heat dissipated therefrom can at times lead to operator discomfort.
Another drawback is that these types of riding platforms position the front of the operators' legs immediately adjacent the hydraulic pumps. A typical stand-on mower incorporates the hydraulic pumps behind the engine, between the rearward portion of the engine and the shins, knees, or other portion(s) of the operator's legs. Some stand-on mowers have a riding platform that extends partially below the hydraulic pumps, whereby parts of the operator's feet are positioned below the pumps during use. This ensures that the operator will stand upon the turning axis, but also requires that part of the operator's legs be adjacent or occasionally even touch portions of the hydraulic pumps. Similar to hydraulic motors, hydraulic pumps become very warm or hot during use, whereby the heat dissipated therefrom can at times lead to operator discomfort.
Other stand-on mowers include riding platforms that position operators behind the mower turning axes, while still presenting various drawbacks. For example, U.S. Pat. No. 5,809,756, entitled “Lawn Mower Usable in Both Riding and Walk-behind Modes,” discloses a riding platform that supports a standing operator behind a turning axis of the mower. The riding platform is hinged at its front edge, connecting it to a rear portion of the mower frame. The hinged attachment of the riding platform allows it to be pivoted up and stowed against the mower while providing adequate clearance between the drive wheels for the operator to walk behind the mower without striding into the riding platform. This configuration requires short platform sidewalls so that the platform can fold up snugly against the mower frame. A drawback of this riding platform is that the short platform sidewalls expose the operator's feet, ankles, and legs to the rotating drive wheels and/or other hazards during use. Operators also have a limited range of positioning relative to the steering devices. The feet of an unusually tall operator and/or an operator with unusually long arms may be positioned in a location that results in substantial discomfort when operating the lawnmower. Simply providing a longer than-usual platform is not an attractive option because a longer platform is more apt to hit the ground when transitioning from level ground to a steep hill or trail or ramp or traveling a curb, potentially damaging the platform or the structure which is contacted by it.
Another drawback is that these types of riding platforms can transfer vibrations, or shock-type or other loads, that are generated by the lawnmower during use or that result from driving the lawnmower across uneven terrain, into the legs and bodies of the operators. Exposure to such vibrations, or shock-type or other loads, can hasten an onset of operator fatigue.